1. Field of the Invention
The embodiments of the present invention relate to a driving circuit of a LCD device, and more particularly to a gate driving circuit, a switching control circuit and a shift register of a LCD device.
2. Description of the Prior Art
Liquid Crystal Display (LCD) has been widely used in various display fields, such as family, public places, offices, and personal electronics-related products. A conventional LCD controls the transmittance of the liquid crystal layer to display an image thereon by the electric field. Therefore, the LCD includes a LCD panel and a driving circuit, wherein liquid crystal cells are arranged in a matrix form in the LCD panel.
When the LCD displays, a signal is outputted by the driving circuit and each pixel is scanned line by line. The drive of the LCD mainly includes a gate driver and a data driver. The data driver latches the inputted display data and clock signal on time sequentially, coverts into an analog signal and then inputs into a data line of the LCD panel, while the gate driver converts the inputted clock signal by a shift register (SR) and switches into an ON/OFF voltage, which is then applied to the gate line of the LCD panel sequentially. The shift register in the gate driver is used for generating the scanning signal in the scanning gate line. Furthermore, the scanning direction of the display device corresponds to the orientation of the LCD, and therefore the orientation of the displayed image may be changed by changing the scanning direction. Accordingly, a LCD with a bi-directional scanning is desired for better facilitating the development of the products.
FIG. 1 is a schematic diagram of a conventional gate driving circuit, which includes a plurality of shift register SR1-SRn, a ground voltage Vss providing line, a first clock CLK providing line, a second clock CLK providing line, and a turn-on pulse STV providing line. Here, the phase of the first clock signal CLK1 is opposite to the phase of the second clock signal CLK2.
When the conventional gate driving circuit operates, if STV=1, a high level pulse is outputted to the input of the first line, and thus the first line turns on, a gate high level is inputted into the panel, and other lines turn off, while an input is injected for the next line thereof, and thus the second line turns on. When the second line outputs a high level, the first line is reset. At this time, all lines turn off except this line, while an input is injected for the next line thereof. Such process is repeated until the last line. Such a circuit only implements the scanning in a particular direction, which cannot satisfy the requirement of changing the orientation of the displayed image.